1. Field of the Invention
The present invention relates to compositions of matter and methods for increasing the cured adhesion strength, hardness and workability of cementitious compositions, such as masonry cements and mortars.
2. Description of the Related Art
Masonry cements and mortars are hydraulic-setting compositions produced particularly for use in bonding of bricks, blocks, and the various components of exterior insulation finishing systems (hereinafter referred to as “EIFS”). Such cements are typically mixed prior to use with a fine aggregate and water. It is desirable that the wet mortar have a high degree of plasticity for working by hand, as well as a relatively a long working time before the cement hardens.
Masonry cements and mortars are produced by grinding Portland cement and gypsum with from about 20 to 65%, of a third material such as limestone, chalk, talc, pozzolans, clay, gypsum, or combinations of such. Portland cement is a type of cement which includes calcined oxides of calcium, aluminum, iron and silicon and is capable of solidifying under water. Such masonry cements are ground to a greater degree of fineness than most Portland cements intended for use in structural concretes. The finer grind of masonry cements improves the plasticity of the finished mortar products.
“Exterior insulation finishing system” or “EIFS” means any one of a number of unique proprietary systems, each of which may consist of specific components associated with a particular EIFS producer. One basic type of EIFS, known as “barrier EIFS”, includes boardstock insulation, reinforced adhesive, and exterior coating arranged in three layers. A less common type of EIFS, known as “drainage EIFS”, may additionally include plastic edge trim, water-resistive barriers, and water drainage cavities. The boardstock is typically expanded polystyrene or extruded polystyrene. One of the persistent problems in EIFS construction is creating a durable and economical adhesive bond between masonry mortar and polystyrene.
The most interior of the three barrier EIFS layers is typically a layer of foam plastic insulation commercially available in the form of polystyrene boardstock. The inner face of the polystyrene boardstock directly contacts a base adhesive (which may be a masonry mortar) and receives mechanical fasteners, such as nails or plugs.
An intermediate adhesive filler layer (which may be a masonry mortar) is applied on the outer face of the polystyrene boardstock insulation, typically by means of a trowel. The adhesive filler layer substantially surrounds and fills a reinforcing mesh, which is embedded in the adhesive filler layer. The mesh is typically made of fiberglass and has openings of about one-quarter inch square. Significantly, preparing the adhesive filler, applying the adhesive filler layer to the outer face of the polystyrene boardstock, and embedding the mesh in the adhesive filler layer are generally considered to be demanding and time-consuming tasks for skilled craftsmen.
The most exterior of the three layers is a called a topcoat. It is normally a colored and textured paint-like material (which may be a masonry mortar) that is applied with a trowel or, less frequently, by spraying. A wide range of colors and textures are available for the topcoat. Available textures include smooth surfaces, rough stucco-like textures, embedded stone chips, granite-like mixtures and brick-like treatments.
U.S. Pat. No. 6,172,147, issued to Abelleira, describes a masonry mortar additive that contains a multi-stage polymer which includes an ionically-soluble polymer stage, and an air entraining agent. The '147 patent lists many exemplary air-entraining agents (referred to collectively in the '147 patent as “AEAs”) as suitable for use in the masonry mortar additive. Among these, listed at Column 4, lines 3-5 of the '147 patent, are anionic AEAs such as sulfosuccinates. In contrast, a spray-dried dialkyl sulfosuccinate salt composition of the present invention acts as a deaerating agent upon mixing with a mineral mortar and water (as set forth below in Example 8).
U.S. Pat. No. 7,204,065, issued to Naji, describes a method for applying a cementitious formulation to a substrate, such as polystyrene, over a confining mesh attached to the substrate. In certain aspects, such as an aspect claimed in claim 25 of the '065 patent, the formulation reportedly includes an air entraining agent (referred to collectively in the '065 patent as “AEAs”). Among these, listed at Column 6, lines 56-59 of the '065 patent, are anionic AEAs such as sulfosuccinates. In contrast, a spray-dried dialkyl sulfosuccinate salt composition of the present invention acts as a deaerating agent upon mixing with a mineral mortar and water (as set forth below in Example 8).
Canadian Patent 491099, issued to Vitalis, describes surface-active dialkyl sulfosuccinates compositions that are prepared in the form of dry, non-caking water-soluble powders by spray-drying with sodium benzoate as a hardener at 600-700 degrees F. However, the '099 patent compositions are not panaceas and may yet be improved upon because, among other reasons, they contain sodium benzoate. One objection to the '099 patent compositions is that sodium benzoate absorbs water in humid atmospheres, and caking and clumping may be expected if the ambient humidity exceeds 50%. Another objection to the '099 patent compositions is that sodium benzoate has been associated with skin and eye irritation in dry atmospheres.
A need exists for an improved solid surfactant that flows freely under humid atmospheric conditions and dissolves quickly in water. Preferably, the new solid surfactant will strengthen adhesive bonding between masonry mortars and smooth, hydrophobic surfaces such as those used in EIFS. Ideally, the new solid surfactant will increase the hardness and reduce the water uptake of masonry cements and mortars.